1. Field of the Invention
The present invention relates to an electric brake actuator incorporated in a vehicle brake system, and to the vehicle brake system.
2. Description of the Related Art
Conventionally, the brake boosters using the vacuum servo and the hydraulic booster are known as vehicle brake mechanisms. Recently, electric brake boosters which use an electric motor as a boosting power source have been disclosed, for example, in Japanese Patent Laid-open No. 2010-23594 (which is hereinafter referred to as JP 2010-23594A).
The electric brake booster disclosed in JP 2010-23594A is a single integrated apparatus having a main piston, a booster piston, and an electric motor. The main piston moves back and forth in response to manipulation of a brake pedal. The booster piston has a cylindrical shape, and is fit onto the main piston in such a manner that the booster piston can move relative to the main piston. The electric motor makes the booster piston move back and forth.
In the above electric brake booster, the main piston and the booster piston operate as pistons of the master cylinder, and the front ends of the main piston and the booster piston are inserted into a pressure chamber of the master cylinder, so that an input thrust applied to the main piston by the brake pedal and a booster thrust applied to the booster piston by the electric motor cause hydraulic brake pressure in the master cylinder.
However, the above electric brake booster disclosed in JP 2010-23594A tends to be large in size, and lacks versatility when the electric brake booster is mass produced.
The present invention has been developed in view of the above circumstances. The object of the present invention is to provide an electric brake actuator and a vehicle brake system having increased versatility.